In various electronic apparatuses such as a computer, a DRAM (Dynamic Random Access Memory) that can be operated at high speed and is capable of recording information with a high density is widely used as a storage apparatus. However, in recent years, a nonvolatile memory that retains recorded information even when power is turned off is starting to be used in various fields in place of the DRAM which is a volatile memory in which recorded information is deleted when power is turned off.
An MRAM (Magnetoresistive Random Access Memory) is known as the nonvolatile memory capable of recording at high speed. As the MRAM, a configuration that uses a giant magneto resistive (GMR: Giant Magneto Resistive) device and a configuration that uses a magnetic tunnel junction (MTJ: Magnetic Tunnel Junction) device are known.
The MRAM that uses the MTJ device is called STT (Spin Transfer Torque)-MRAM. Since the STT-MRAM includes a higher magnetoresistance change rate (MR ratio) than the MRAM that uses a GMR device, high-intensity readout signals can be generated. Technologies related to the STT-MRAM are disclosed in, for example, Patent Literatures 1 to 4 and Non-patent Literatures 1 to 4.
As an STT-MRAM recording system, there are an in-plane magnetization system and a perpendicular magnetization system in which magnetization directions mutually differ between MTJ devices. In recent years, an STT-MRAM of a perpendicular magnetization system, that can be made more compact and set to have a large capacity is attracting attention. In a recording operation of the STT-MRAM of a perpendicular magnetization system, by performing a spin injection by causing a current to flow through each MTJ device, a perpendicular magnetization of a storage layer in each of the MTJ devices is inverted. In the STT-MRAM, binary information (typically, “0” and “1”) can be recorded on the basis of directions of the perpendicular magnetizations in the MTJ devices.